Generation of gaseous mixtures for inflatable devices



Feb. 25, 1964 L. v. HEBENSTREIT ETAL 3,122,181

GENERATION OF GASEOUS MIXTURES FOR INFLATABLE DEVICES Filed Nov. 3, 1961 Fig.l

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D Evi CE GENERATOR ASPIRATOR l INVENTORS LESTER V- HEBENSTREIT BYCHARLES A.H Ems ATTO R N EY United States Patent O 3,122,181 GENERATIN F GASEQUS MIXTURES FCR WFLATABLE DEVICES Lester V. Hebenstreit, Bloomfield, and Charles A. Heins,

Clifton, NJ., assignors to Specialties Development Corporation, Belleville, NJ., a corporation of New Jersey Filed Nov. 3, 1961, Ser. No. 149,895 3 Claims. (Cl. 141-4) The invention relates to inating inflatable devices, and, more particularly, to a method of generating gaseous mixtures of carbon dioxide and combustion products of propellants and inflating such devices.

Heretofore, various types of inflatable devices have been used extensively by the armed forces including landing pads for helicopters and flotation equipment such as rafts, boats, escape ladders and the like. For many years, liquefied carbon dioxide has been considered one of the best sources of pressure media for inilating such devices because of its high storage density, relatively low storage pressure, nonflammability and low toxicity, and because of its ability to be discharged at temperatures as low as 65 F. when confined in a container having a gas such as nitrogen added thereto.

However, when carbon dioxide,`after being stored at a low temperature, is rapidly introduced into and is expanded in a relatively large inflatable bag or envelope, it produces carbon dioxide snow and cold carbon dioxide gas with the result that full ination cannot be attained within the short period of time required in an emergency.

Accordingly, an. object of the present invention is to provide a method of rapidly inflating equipment with carbon dioxide which has been stored at low temperatures.

Another object is to provide such a method which is suitable for a closed system or a system wherein ambient air is entrained.

Another object is to accomplish the foregoing in a simple, practical, reliable and economical manner.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

in accordance with the present invention, it has been discovered that the foregoing objects can be generally accomplished by mixing the hot gaseous combustion products of propellants such. as burning powders with liquefied carbon dioxide, whereby the hot gases heat and gasify the carbon dioxide to attain a desired pressure and the subsequent expansion of the carbon dioxide produces a cooling effect which reduces the temperature of the hot gases so that the mixture is at a temperature which the inflatable equipment can withstand.

lt is contemplated that the amount of heat to be produced for each pound of carbon dioxide at a given temperature can be predetermined for summertime or high ambient temperature operation (e.g. 20 F. to 125 F.) and for Wintertime or low temperature operation (c g. 20 F. to 80 F), as will be explained hereinafter with reference to the specic examples of the present invention.

A preferred embodiment of apparatus for carrying out the invention has been chosen for purposes of illustration and description, and is shown in the accompanying drawing, forming a part of the specification, wherein:

FIG. l is a schematic view of a closed system utilizing apparatus for producing a gaseous mixture in accordance with the present invention for inflating an inflatable device.

FIG. 2 is an enlarged longitudinal sectional view, partly in elevation, of the apparatus for producing the gaseous mixture.

3,122,181 Patented Feb. 25, 1964 ICC FIG. 3 is a schematic View of a system wherein ambient air is entrained with the gaseous mixture.

Referring now to FIGS. 1 and 2 of the drawing in detail, a closed system is shown in FIG. l which comprises an inflatable device itl, a gas generator 11, and a conduit 12 for directly conducting a mixture of gases from the gas generator to the inflatable device. Such a closed system can operate in the air or under water.

The inflatable device 10 may be a bag of any desired shape and size used in connection with boats, rafts, rescue devices or helicopter landing pads.

The interior of the gas generator 11 for producing the mixture of gases is shown in FlG. 2. The gas generator comprises a container 15 for confining carbon dioxide; an outlet assembly 16 having the conduit 12 connected to its outlet 17; a pressure rupturable disc 18 for normally sealing the container to prevent discharge through the outlet; a hot gas generating chamber 19 including a charge 2t? of propellant adjacent the outlet, an electrically actuated squib 21 for igniting the charge, and passageway means 22 for conducting the het gases from the chamber to the interior of the container 15 for admixture with the carbon dioxide; and a safety disc assembly 24 adapted to burst in the event an unsafe pressure is created Within the container.

In operation, the squib 2,1 is actuated to ignite the charge 2li, and the propellant generates hot gases which are admixed with the carbon dioxide to increase the pressure within the container 1S and burst the disc 1S. This mixture is discharged through the outlet 17 and is conducted by the conduit 12 to the inflatable device 10 or other point of use. As this occurs, the hot gases increas-e the pressure of the carbon dioxide and the carbon dioxide upon expansion cools the hot gases by the Joule- Thomson eifect which takes place when it is suddenly expanded from a high pressure to a much lower pressure, whereby the temperature of the mixture which enters the inflatable device is neither too high to harm the bag nor too low to allow the formation of carbon dioxide snow particles to take place within the bag.

Numerous tests have indicated that, at ambient temperatures between 26 and 125 F., the temperature of the gaseous mixture in the bag can be controlled by varying the ratio of the number of Btu. produced for each pound of carbon dioxide. This ratio is higher at the lower ambient temperature than at the higher ambient temperatures. For example, at 20 F. about 154 Btu. may be generated by the propellant for each pound of carbon dioixde, and at F. about 144 Btu. may be generated by the propellant for each pound of carbon dioxide.

A propellant charge which has been found suitable is a potassium perchlorate type powder capable of producing about 1740 Btu. a pound. Thus, by varying the weight of the charge, the desired number of Btu. to be produced can be predetermined within accurate limits.

As specific examples of the present invention a 56 cubic foot bag for a helicopter pad was inflated to a pressure of about three p.s.i.g. in less than four seconds by a hot gas generator container 11 having a volume of about 329 cubic inches and containing the following amounts of material:

ExamphI I Working temperature range F 20 to 80 Carbon dioxide pounds 7.33 Charge 2b do 0,65 Bag temperature after iniiation:

Maximum F 300 Minimum F 20 Example II Working temperature range F- 20 to 125 Carbon dioxide pounds 6.78 Charge 2@ do 0.56 Ba g temperature after inilation:

Maximum F- 3 05 Minimum F 2() Since the bag during or immediately after inflation rests on a body of Water and is partially submerged therein, there is a rapid heat exchange between the gases and the water to immediately lower the higher temperatures of the gaseous mixture being generated and to raise the lower temperatures or" the gaseous media introduced into the intlatnble device, whereby damage to the bag is averted.

(Ether tests indicated that the mixture in accordance with the foregoing examples are also suitable for inating flotation equinment, particularly such equipment having a relatively large bag volume.

in FiG, 3, a system is shown which comprises an inlatable device 1d, a gas generator 11 such as described with reference to FlG. 2, a conduit 12 for conducting the gaseous mixture from the generator to the device, and a device 1.3 connected in the conduit for entraining ambient air and introducing the air into the inilatable device.

Such a system further reduces the temperature of a hot gaseous mixture during ination and increases the amount of gaseous media introduced into the inflatable device. Such a system is suitable for use Where underwater operation is not required.

The air entraining device 13 may be of a conventional design. such as shown in United States Patent No. 2,- 975,958.

From the foregoing description, it will be seen that the present invention provides a simple, practical and economical method of inllating inflatable devices throughout a wide range of temperatures.

Tt will be understood that the details and examples hereinbefore set forth are illustrative only and that the invention as broadly described and claimed is in no way limited thereby.

We claim:

l. The method of inating an inflatable device, which method comprises generating a predetermined charge of hot gases under pressure in a confined zone, mixing the gases with a predetermined charge of carbon dioxide under pressure in the Zone to increase the pressure of the carbon dioxide, releasing the mixture of gases and carbon dioxide from the Zone, expanding the released pressurized carbon dioxide in admixture with the gases to cool the gases, and introducing the expanded mixture into the inflatable device, the quantitative relationship of the charge of carbon dioxide and the charge of hot gases being such so as to produce the expanded mixture at temperatures and pressures suitable for introduction into the inflatable device.

2. The method according to claim 1, including entraining ambient air with the mixture of gases and carbon dioxide and introducing the same with said mixture into the inilatable device.

3. The method according to claim 1, wherein a suiiicient amount of hot gases is generated to produce between about 144 and about 154 Btu. for each pound of carbon dioxide.

References Cited in the tile of this patent UNITED STATES PATENTS 164,818 Duc lune 22, 1875 928,801 Bargar June 8, 1909 1,008,646 Kassner Nov. 14, 1911 1,328,088 Lutz lan. 13, 1920 1,339,431 Backhaus May 11, 1920 1,659,384 Thomas Feb. 14, 1928 2,028,651 Dagnall et al Jan. 21, 1936 2,349,480 Walk May 23, 1944 2,478,958 Wheeler et al. Aug. 16, 1949 2,687,541 Bannister Aug. 31, 1954 2,989,381 Musser June 20, 1961 

1. THE METHOD OF INFLATING AN INFLATABLE DEVICE, WHICH METHOD COMPRISES GENERATING A PREDETERMINED CHARGE OF HOT GASES UNDER PRESSURE IN A CONFINED ZONE, MIXING THE GASES WITH A PREDETERMINED CHARGE OF CARBON DIOXIDE UNDER PRESSURE IN THE ZONE TO INCREASE THE PRESSURE OF THE CARBON DIOXIDE, RELEASING THE MIXTURE OF GASES AND CARBON DIOXIDE FROM THE ZONE, EXPANDING THE RELEASED PRESSURIZED CARBON DIOXIDE IN ADMIXTURE WITH THE GASES TO COOL THE GASES, AND INTRODUCING THE EXPANDED MIXTURE INTO THE INFLATABLE DEVICE, THE QUANTITATIVE RELATIONSHIP OF THE CHARGE OF CARBON DIOXIDE AND THE CHARGE OF HOT GASES BEING SUCH SO AS TO PRODUCE THE EXPANDED MIXTURE AT TEMPERATURES AND PRESSURES SUITABLE FOR INTRODUCTION INTO THE INFLATABLE DEVICE. 